Abstract
Cold damage is a threat to grapegrowers worldwide. Cold hardiness varies across Vitis vinifera cultivars, but the influence of clone and rootstock selection on this trait is unclear. Five clone x rootstock combinations of Riesling (clone 49 x Riparia Gloire (RG); 49 x SO4 Teleki; clone 239 x RG; 239 x SO4; 239 x Couderc 3309) and four clones of Sauvignon blanc (clone 242, 297, 376, and 530 on SO4 Teleki rootstock) were evaluated over three dormant seasons (2016/17, 2017/18, and 2018/19). Bud cold hardiness was quantified every two to four weeks by differential thermal analysis (DTA) and reported as low temperature exotherms (LTE). Yield and pruning weights were recorded every year. Rootstock did not consistently influence the cold hardiness of Riesling buds, although clone 239 was generally hardier than clone 49. Significant clone*rootstock interactions were observed more frequently in the first year of the study. No consistent differences were observed between Sauvignon blanc clones, although clone 242 and 297 were often amongst the least hardy clones. Differences in hardiness were not consistently related to yield, pruning weight or crop load in the prior growing season. This study demonstrates the importance of both clone and rootstock selection in cool climate regions where freeze injury may occur. Future research should consider the clone identity and the possibility of a clone x rootstock interaction when comparing the cold hardiness of different cultivars.
Highlights
Cold damage is a threat to grapegrowers worldwide
The 2016/17 dormant season was preceded by the lowest total rainfall, with only 207 mm received from May to October and long periods without rainfall in May, June, and July (Figure 1)
This study investigated the cold-hardiness of Riesling and Sauvignon blanc by evaluating five clone × rootstock combinations of Riesling and four clones of Sauvignon blanc using differential thermal analysis (DTA) over three dormant seasons
Summary
Cold damage is a threat to grapegrowers worldwide. Cold hardiness varies across Vitis vinifera cultivars, but the influence of clone and rootstock selection on this trait is unclear. Rootstock did not influence the cold hardiness of Riesling buds consistently, clone 239 was generally hardier than clone 49. Differences in hardiness were not consistently related to yield, pruning weight, or crop load in the prior growing season. This study demonstrates the importance of both clone and rootstock selection in cool climate regions where freeze injury may occur. Grapevine cold hardiness depends on supercooling, which is the capacity to prevent freezing of intracellular water (Pierquet et al 1977). This ability develops during endodormancy, which is first initiated by a shorter photoperiod and enhanced by decreasing temperatures (Schnabel and Wample 1987). Acclimation is accompanied by periderm formation around the canes and de-
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